Pulling membrane stent delivery system

ABSTRACT

A medical device delivery system, having a rolling retractable sheath covering a medical device mounting region on the system is disclosed. The rolling retractable sheath comprises an inner wall and an outer wall and may be formed of one or more materials, optionally porous. Optionally, a lubricant may be applied selectively to the interior and exterior walls of the stent.

This application is a Continuation application from U.S. applicationSer. No. 09/187,947 filed Nov. 6, 1998 now U.S. Pat. No. 6,059,813, thecontents of which is hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to a stent delivery catheter system, such as thekind used in percutaneous transluminal coronary angioplasty (PTCA)procedures. More particularly, it relates to a stent delivery catheteremploy a rolling retractable sheath which may be retracted to release aself-expanding or balloon expandable stent.

BACKGROUND OF THE INVENTION

In typical PTCA procedures, a guiding catheter is percutaneouslyintroduced into the cardiovascular system of a patient and advancedthrough the aorta until the distal end is in the ostium of the desiredcoronary artery. Using fluoroscopy, a guide wire is then advancedthrough the guiding catheter and across the site to be treated in thecoronary artery. An over the wire (OTW) balloon catheter is advancedover the guide wire to the treatment site. The balloon is then expandedto reopen the artery. The OTW catheter may have a guide wire lumen whichis as long as the catheter or it may be a rapid exchange catheterwherein the guide wire lumen is substantially shorter than the catheter.Alternatively, a fixed wire balloon catheter could be used. This devicefeatures a guide wire which is affixed to the catheter and cannot beremoved.

To help prevent arterial closure, repair dissection, or preventrestenosis, a physician can implant an intravascular prosthesis, or astent, for maintaining vascular patency inside the artery at the lesion.The stent may either be a self-expanding stent or a balloon expandablestent. For the latter type, the stent is often delivered on a balloonand the balloon is used to the expand the stent. The self-expandingstents may be made of shape memory materials such as nitinol orconstructed of regular metals but of a design which exhibits selfexpansion characteristics.

In certain known stent delivery catheters, a stent and an optionalballoon are positioned at the distal end of the catheter, around a corelumen. The stent and balloon are held down and covered by a sheath orsleeve. When the distal portion is in its desired location of thetargeted vessel the sheath or sleeve is retracted to expose the stent.After the sheath is removed, the stent is free to self-expand or beexpanded with a balloon.

A number of sheath designs are known in the art including thosedisclosed in U.S. Pat. No. 4,732,152 to Wallsten ('152), U.S. Pat. No.4,848,343 to Wallsten ('343), U.S. Pat. No. 4,875,480 to Imbert, U.S.Pat. No. 5,662,703 to Yurek et al. ('703), U.S. Pat. No. 5,690,644 toYurck ('644) and WO 94/15549, all of which disclose using a sleeveformed of a doubled-over section of membrane to compress and contain thestent.

Wallsten '152 and Wallsten '343 disclose the use of lubricants on theinterior walls of the membrane. Moreover, fluid may be introduced intothe chamber that is formed, in part, by the walls of the doubled-overmembrane.

The Imbert device contains small holes in the sleeve to allow for theexpulsion of gas therefrom upon the introduction of a fluid into theregion between the inner and outer walls. The holes are not sized toallow for fluid flow therethrough.

Yurek '703 discloses a stent that is retained distal to the inner tubeby a folded over sheath. The outer layer of the sheath, although not theinner layer, is disclosed as being porous. The Yurek '644 patent and WO94/15549 disclose a catheter in which a stent is mounted on an innertube and retained by a double walled hose having micropores in the outerwall of the hose. The micropores allow for the flow of fluidtherethrough. The Yurek catheter is of the rapid-exchange design.

U.S. Pat. No. 5,445,646 to Euteneuer et al., incorporated herein in itsentirety by reference, discloses a stent delivery apparatus comprising asingle layer sheath retaining sleeve means for retaining the stent inits delivery configuration attached to a slipping sleeve means forreleasing the stent to self-expand. The slipping sleeves may beactivated hydraulically by delivering a fluid to the area in between theinner and outer layers of the slipping sleeve.

While the use of rolling membranes is known, it is desirable to providea medical device delivery system with a rolling retractable sheath inwhich the frictional interactions between the inner and outer walls ofthe sheath are reduced without requiring hydraulic activation. A rollingmembrane eliminates the problem of sliding friction that is common withsliding sheaths as the rolling membrane, literally, rolls off of thestent. This, in turn, results in a lesser likelihood of the stent beingdamaged as the sheath is removed from over it. It is also desirable toprovide such a system with a sealed rolling retractable sheath toprevent any lubricants interior to the sheath from interacting with anybodily fluids. It is also desirable to provide such a system having arolling retractable sheath whose inner and outer walls exhibitsdifferent physical properties such as hoop strength and creepresistance. The creep resistance of the outer wall is of particularvalue in preventing the stent from growing in profile and therebydeforming the catheter sheath. Finally, it is desirable to provide amedical device delivery system which is self-priming.

The present invention addresses these needs in its various embodimentsas described below.

SUMMARY OF THE INVENTION

The present invention provides a medical device delivery system whichcomprises an inner tube having a medical device mounting region at thedistal region for concentrically mounting a medical device thereon and arolling retractable sheath for retaining a medical device on the innertube and a retraction device.

The rolling retractable sheath, which includes a rolling double walledmember, may be formed of a single member folded over on itself or of twodifferent members joined together and folded over on itself. It isdisposed concentrically about the inner tube. The inner wall of thedouble walled member is attached to the inner tube proximal to themedical device mounting region and the outer wall of the double walledmember is attached to a retraction device. The inner wall has a greatertendency to rollingly move upon the application of a rolling force thanthe outer wall.

A sealed chamber may optionally be formed by the inner and outer wallsof the sheath, at least a portion of the inner tube and the portion ofthe retraction device which is distal to the point of attachment of theouter wall to the retraction device. The sheath is retractable from adelivery position to a release position. In the delivery position, thesheath covers at least a portion of the medical device mounting regionwhile in the release position, the sheath no longer covers the medicaldevice mounting region.

The retraction device, which is operably connected to the rollingretractable sheath for retraction of the retractable sheath, moves theouter wall in a proximal direction relative to the inner wall so thatthe sheath no longer covers the medical device mounting region.

In another embodiment, the invention provides a self-priming medicaldevice delivery system comprising an inner tube, a rolling retractablesheath for retaining a medical device on the inner tube and a retractiondevice operably connected to the rolling retractable sheath forretraction of the retractable sheath.

The inner tube has a medical device mounting region at the distal regionfor concentrically mounting a medical device thereon. The rollingretractable sheath, formed of a material porous enough to allow fluidsthrough, is disposed concentrically about the inner tube and includes arolling double walled member. The inner wall of the rolling retractablesheath is attached to the inner tube proximal to the medical devicemounting region while the outer wall is attached to a retraction device.In the delivery position, the sheath covers at least a portion of themedical device mounting region while in the release position the sheathno longer covers the medical device mounting region.

The retraction device is operably connected to the rolling retractablesheath for retraction of the retractable sheath, moving the outer wallin a proximal direction relative to the inner wall.

In yet another embodiment, the invention is directed to medical devicessuch as those described above in which the inner wall of the retractablesheath is flexible enough to roll while the outer wall of theretractable sheath is stiff enough to prevent unwanted movement of thesheath.

In yet another embodiment, the invention is directed to a medical devicesuch those described above in which the inner wall of the rollingretractable sheath is formed of at least a first material and the outerwall is formed of at least a second material different from the firstmaterial. The inner and outer walls may be adhesively bonded together,mechanically joined together or otherwise joined to each other.

In another embodiment, the inner and outer walls, respectively, may beconstructed of a first material which rolls on retraction of the sheathand a second material which does not roll on retraction. In anotherembodiment the second material has a higher hoop strength than the firstmaterial. In yet another embodiment the outer wall material has a highertensile strength than the inner wall material of the sheath. In yetanother embodiment the outer wall exhibits a higher degree oflongitudinal stiffness than the inner wall. In yet another embodimentthe outer wall exhibits a higher flexural modulus than the inner wall.

In the above embodiments where the inner and outer walls are made ofdifferent materials, the thickness of the inner and outer walls may alsodiffer, further contributing to the desired properties of the walls.

In yet another embodiment of the invention, the inner and outer wallsare made of the same material, the inner wall being thinner than theouter wall. The inner wall is thin enough to allow the inner wall toroll while the outer wall is sufficiently thick to resist rolling andprevent unwanted movement of the stent. Desirably, the thickness of theouter wall will be at least 1.5 times the thickness of the inner wall.more desirably, the outer wall will be at least 4 times the thickness ofthe inner wall.

In the above embodiments, the first and/or second wall materials mayoptionally be porous enough to allow a fluid to pass therethrough.

In all of the above embodiments, a lubricant may, optionally, applied toat least a portion of the inner wall and/or outer wall.

Further, in all of the above embodiments, a pull-collar mounted at thedistal end of the catheter in conjunction with a pull wire may beemployed as part of the retraction device.

The invention is further directed to a stent delivery device comprisingany of the above-described medical device delivery systems with a stentmounted on the medical device mounting region of the inner tube. Otherdevice that may be delivered by the above described systems includegrafts and vena cava filters.

The invention is also directed to a method of delivering a medicaldevice to a desired bodily location. The method comprises the steps ofproviding medical device delivery system and a medical device, mountingthe medical device on the medical device mounting region of one of thedescribed medical device delivery systems, percutaneously inserting themedical device delivery system in a bodily lumen containing a bodilyfluid, the bodily fluid passing through the sheath so as to prime themedical device delivery system, traversing the bodily lumen until thedesired bodily location is reached, retracting the rolling retractablesheath proximally so as to expose medical device and withdrawing themedical device delivery system from the bodily lumen. In a preferredembodiment, the medical device is a stent, optionally self-expanding,although other devices including grafts and vena cava filters may besimilarly delivered.

Finally, the invention is directed to a medical device delivery systemcomprising an inner tube having a medical device mounting region at thedistal region for concentrically mounting a medical device thereon, arolling retractable sheath and a retraction device for retracting therolling sheath. The rolling retractable sheath serves to retain amedical device on the inner tube. The rolling retractable sheath isformed of a sealed rolling double walled member which is disposedconcentrically about the inner tube. At the proximal end, the rollingsheath is secured, directly or indirectly via a bumper or othersecurement device, to the inner tube proximal of the medical devicemounting region. At the distal end, the rolling sheath is attached to aretraction device.

For the purposes of this disclosure, it should be noted that the term“medical device mounting region” is intended to apply to a region of aninner tube on which a medical device resides as well as a region of aninner tube over which a medical device resides. An example of the formeris a region of an inner tube to which a stent is crimped. An example ofthe latter is a region over which a self expanding stent resides.Moreover, where reference is made to mounting a medical device on aninner tube, it is intended to include both mounting the device on andmounting the device over the inner tube.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1a shows a schematic longitudinal cross-sectional view of inventivemedical device delivery system.

FIG. 1b shows a partial exploded view of circled region 1 b in FIG. 1a.

FIG. 2 shows the distal end of the inventive medical device deliverysystem of FIG. 1 with the rolling retractable sheath in a retractedposition.

FIG. 3 shows a schematic longitudinal cross-sectional view of the distalend of an inventive medical device delivery system

FIG. 4 shows a schematic longitudinal cross-sectional view of the distalend of an inventive medical device delivery system.

FIGS. 5a and 5 b shows schematics of rolling retractable sheaths for usein the present invention.

FIG. 6 shows a schematic longitudinal cross-sectional view of the distalend of an inventive medical device delivery system.

FIGS. 7a and 7 b are schematic longitudinal cross-sectional views of adouble walled sheath before and after retraction.

FIGS. 7c and 7 d are schematic longitudinal cross-sectional views of asealed double walled sheath before and after retraction.

FIG. 8 shows a suitable stent for use with the inventive medical devicedelivery system.

FIG. 9 shows a suitable graft for use with the inventive medical devicedelivery system.

FIG. 10 shows a suitable vena cava filter for use with the inventivemedical device delivery system.

DETAILED DESCRIPTION OF THE INVENTION

While this invention may be embodied in many different forms, there aredescribed in detail herein specific preferred embodiments of theinvention. This description is an exemplification of the principles ofthe invention and is not intended to limit the invention to theparticular embodiments illustrated.

Referring to the figures, FIG. 1a shows an inventive medical devicedelivery system in general at 110. At the distal end of inner tube 114is a medical device mounting region 118. Inner tube 114 is desirablymade of flexible, but incompressible construction such as a polymerencapsulated braid or coil. The flexibility of the braid/coilconstruction allows the medical device delivery system to navigatethrough body lumens and the incompressibility of the braid/coil aids inmaintaining the integrity for the catheter and aids in deploymentaccuracy when the retractable rolling sheath is being retracted duringstent release. The braid/coil may be comprised of stainless steelencased in a polymer such as Polyimide with an inner layer of Teflon.The inner tube need not, however, be made of incompressible materials.Flexible and compressible materials such as polyethylene may also beused.

Covering medical device mounting region 118 is a rolling retractablesheath 122 for retaining a medical device on the inner tube. The medicaldevice delivery system further comprises a retraction means forretracting the rolling retractable sheath.

Rolling retractable sheath 122, disposed concentrically about inner tube114, is formed of a single material folded over on itself. As such, atleast a portion of the sheath is double-walled. Inner wall 130 of sheath122 is attached to inner tube 114 at a region 134 proximal to medicaldevice mounting region 118. Outer wall 138 of sheath 122 is attached toretraction device 126 at region 142 of the retraction device. A sealedchamber 146 is formed by inner wall 130 and outer wall 138 of thesheath, at least a portion 150 of the inner tube and the portion 154 ofthe retraction device which is distal to the region of attachment 142 ofthe outer wall to the retraction device. The sheath is retractable froma delivery position, as shown in FIG. 1a, to a release position as shownin FIG. 2. In the delivery position, the sheath covers at least aportion of the medical device mounting region while in the releaseposition, the sheath no longer covers the medical device mountingregion.

A retraction device 126 is attached to rolling retractable sheath 122.Retraction device 126 comprises a pull collar 127 operably attached to apull-wire 128 which extends to the proximal end of the medical devicedelivery system. Pull collar 127 is a ring-shaped member of stainlesssteel or preferably of a radio-opaque material such as gold affixed todistal outer tube 178 by an appropriate adhesive such as a urethane. Thedistal outer tube is, in turn, connected to the rolling sheath. The pullwire may be made of suitable material including stainless steel.

The inventive medical device delivery system, optionally, furthercomprises a collapsible midshaft sheath, as shown in FIG. 1a and in moredetail in FIG. 1b. The distal end of proximal outer tube 170 isattached, desirably adhesively bonded, to an accordion-like collapsiblemidshaft sheath 174. The distal end of collapsible midshaft sheath 174is, in turn, attached, desirably adhesively bonded, to distal outer tube178. Pull collar 127 is attached to the distal end of distal outer tube178. In operation, the retraction device moves the outer wall in aproximal direction relative to the inner wall so that the sheath nolonger covers the medical device mounting region. In so doing,collapsible midshaft sheath 174 decreases in length. Additionalinformation about the collapsible midshaft sheath made be found in U.S.Pat. No. 5,534,007 to St. Germain and Olson, incorporated herein in itsentirety by reference.

Rolling retractable sheath 122 is retractable from a delivery positionas shown in FIG. 1, to a release position as shown in FIG. 2.

As seen in FIG. 1a, the medical device delivery system further comprisesan optional tip 162 mounted at the distal end of inner tube 114 abuttingretractable sheath 122. Tip 162 may be affixed to the inner tube by anadhesive such as H.B. Fuller 3507, a urethane adhesive, or the like.

Also shown in the embodiment of FIG. 1a is a self-expanding stent 158mounted on medical device mounting region 118 of the system. Stent 158is contained in medical device containment area 166.

Because sealed chamber 146 is not in fluid communication with any partof the delivery system proximal of the sheath, the sealed chamber may becoated or filled with a lubricating substance to reduce the frictionbetween the inner and outer walls of the sheath without any directinteraction between the lubricating substance and a bodily fluid.

In another embodiment of the invention, as shown in FIG. 3, the medicaldevice delivery system shown generally at 210 comprises an inner tube214 with a medical device mounting region 218 at the distal end of innertube. Covering medical device mounting region 218 is a rollingretractable sheath 222 for retaining a medical device on the inner tube.Attached to rolling retractable sheath 222 is a retraction device 226for retracting the sheath.

As in the previous embodiment, rolling retractable sheath 222, is formedof a single material folded over on itself. Inner wall 230 of sheath 222is attached to inner tube 214 at a region 234 proximal to medical devicemounting region 218. Outer wall 238 of sheath 222 is attached toretraction device 226 at region 242 of the retraction device. As before,retraction device 226 includes proximal outer tube 270 attached toretractable sheath 274 which in turn is attached to distal outer tube278. Pull collar 227 is attached to the distal end of the distal outertube 278 and pull wire 228 extends proximally from pull collar 227.

Also shown in the embodiment of FIG. 3 is an optional self-expandingstent 258 mounted on medical device mounting region 218 of the system.Stent 258 is contained in medical device containment area 266.

Although sheath 274 in the unretracted position, as shown in FIG. 3, isshown as being double walled over the entire length of stent 258, thedouble walled region of the sheath need not extend over the entirelength of the stent but may extend over only a fraction of the stent.Using a sheath whose doubled over region in the unretracted position isof reduced length may prove advantageous in that the overall length ofthe sheath in the retracted position is also reduced thereby resultingin a delivery system with a smaller profile over a greater length. It isdesirable for the double over region to extend over at least one-half ofthe stent and more desirable to extend over at least one quarter or oneeighth of the stent.

Optionally, the chamber 246 formed by inner wall 230 and outer wall 238of the sheath and at least a portion of the inner tube 250 and a portionof the retraction device 226 may be sealed.

As seen in FIG. 3, the medical device delivery system further comprisesan optional tip 262 mounted at the distal end of inner tube 214 abuttingretractable sheath 222.

In the embodiment shown in FIG. 3, the rolling sheath 222 is made, atleast in part, of a porous material capable of allowing fluidtherethrough. Suitable porous materials include expandedpolytetrafluoroethylene (ePTFE) and polyester. Desirably, the materialswill have a pore size ranging from 0.01 mm to 5.0 mm.

The porosity of the inner and outer walls allows medical devicecontainment area 266 to be flushed free of air by fluid travelingthrough the inner and outer walls and into the medical devicecontainment area.

In yet another embodiment, as shown in FIG. 4, the inventive medicaldevice delivery system, shown generally at 310, is constructed similarlyto the embodiment of FIG. 2, differing in that rolling sheath 322 has aninner wall 330 and an outer wall 338, the inner wall formed of at leasta first material, and the outer wall formed of at least a secondmaterial different from the first material. The delivery system of FIG.4 further differs from the delivery system of FIG. 3 in that inner tube318 is comprised of part of a dual lumen tube. The other lumen 382 ofthe dual lumen tube provides for a flush lumen in fluid communicationwith stent chamber 386.

As before, retraction device 326 includes proximal outer tube 370attached to retractable sheath 374 which in turn is attached to distalouter tube 378. Pull collar 327 is attached to the distal end of thedistal outer tube 378 and pull wire 328 extends proximally from pullcollar 327.

As seen in FIG. 4, the medical device delivery system further comprisesan optional tip 362 mounted at the distal end of inner tube 314 abuttingretractable sheath 322.

Also shown in the embodiment of FIG. 3 is a self-expanding stent 358mounted on medical device mounting region 318 of the system. Stent 358is contained in medical device containment area 366. Optional bumper 372is also shown. Bumper 372 may be of polyethylene and is affixed to theinner tube by an adhesive such as H.B. Fuller 3507.

Additionally, the medical device delivery system may comprise markerbands (not shown) included to aid in positioning and maybe affixed tothe inner tube by adhesive such as Loctite 4011.

Inner wall 330 and outer wall 338 may be adhesively bonded together,heat welded, sutured or otherwise mechanically joined together. Suitableadhesives include urethane and epoxy.

While the invention contemplates a wide variety of choices for first andsecond materials, the materials must be chosen such that the material ofthe inner wall will have a greater tendency to rollingly move upon theapplication of a rolling force than the outer wall. For the purposes ofthis application, the relative tendency of materials to rollingly movemay be tested by taking a strip of a given material, immobilizing oneend of the strip, folding a small portion of the opposite end of thematerial over on itself and measuring the force in the longitudinaldirection necessary to initiate rolling motion of the folded over end ofthe material.

Desirably, a first material that rolls on retraction of the sheath willbe selected along with a second material that does not roll onretraction. Desirably, the second material will have a higher hoopstrength than the first material. Also, desirably, the outer wall of thesheath in the unretracted position has a higher tensile strength thanthe inner wall of the sheath. In a preferred embodiment, the outermaterial is made of high density polyethylene (HDPE) and the innermaterial is made of poly(block-amide-block-ether) ester materials suchas PEBAX™ brand polymers manufactured by Atochem North America, Inc.(Philadelphia Pa.).

The materials may also be chosen so that the outer layer is resistant tocreep in the radial direction and/or resistant to compression orexpansion in the longitudinal direction while the inner layer isflexible, both radially and longitudinally. The extra strength of theouter layer prevents the sheath from creeping under the force of aself-expanding stent contained by the sheath and helps to ensure thatthe stent will not deploy until the system is actuated. At the sametime, the flexibility of the inner layer allows the sheath to be rolledin on itself.

The materials may also be chosen such that the outer layer is made of amaterial of higher tensile strength, flexural modulus and/or higher hoopstrength than the inner layer. The materials may also be chosen suchthat the outer layer has a higher degree of longitudinal stiffness thanthe inner layer.

In another embodiment of the invention, the rolling retractable sheathis characterized by the presence of an outer wall of a first thicknessand an inner wall of a second thickness. The first thickness may begreater or less than the second thickness. Where the outer wall isthinner than the inner wall, the material of the outer wall must have aflexural modulus and/or tensile strength and/or hoop strength and/orlongitudinal stiffness in excess of that of the inner material so thatthe relative thicknesses of the layers is offset by the relativematerial properties of the walls.

The invention also contemplates a medical device delivery system havinga rolling retractable sheath where the inner wall of the retractablesheath is flexible enough to roll while the outer wall of theretractable sheath is stiff enough to prevent unwanted movement of thestent and the outer and inner walls are made of the same material. Theproperty differentiation results from the inner wall being thinner thanthe outer wall. This may be accomplished, for example, by providing atapered tube folded over on itself.

The invention also contemplates the use of porous materials for thefirst and/or second materials. Where both materials are porous, themedical device delivery system will be self-priming. Suitable porousmaterials for use in this embodiment include ePTFE, polyester, andsilicone.

In a more general way, the invention contemplates the use ofthermoplastic elastomers such as polyurethane, polyethylene, polyester,polyvinyl chloride, nylon and their block copolymers as well as PEBAX™polymers for the double walled sheath. Other suitable materials includefluoropolymers, non-compliant polyethylene terephthalate (PET),polyimide and polyolefin copolymers such as SURLYN™.

Typically, the materials for use in the double walled sheaths of theinvention will exhibit high strength even for wall thicknesses as smallas 1/1000's of an inch. Suitable materials include uniaxially orientedfilms such as are formed by blow molding.

In order to reduce friction between the outer and inner walls, asuitable lubricant, as is known in the art, may be selectively appliedto at least a portion of the inner and/or outer walls. The inventionalso contemplates completely covering the inner and outer walls with alubricant. Suitable lubricants include silicones, polyvinyl pryoladone,and PPO (polypropylene oxide). Additionally, BioSlide™ coating producedby SciMed made be used as well. BioSlide™ is a hydrophilic, lubriciouscoating comprising polyethylene oxide and neopentyl glycol diacrylatepolymerized in a solution of water and isopropyl alcohol in the presenceof a photoinitiator such as azobisisobutronitrile. Other hydrogels suchas PEG (polyethylene glycol) and Pluronic (a PEO/PPO/PEO - polyethyleneoxide/polypropylene oxide/polyethylene oxide triblock polymermanufactured by BASF) may also be used. Fluids, desirablybio-compatible, may also be used as lubricants in the practice of theinvention. The presence of a fluid between the inner and outer walls ofthe sheath prevents the inner and outer walls from contacting oneanother thereby reducing the friction between the walls.

Friction between the inner and outer walls may also be reduced byaltering the design of the rolling sheath. The rolling sheath shown inthe above figures is reproduced in FIG. 5a. Inner wall 430 and outerwall 438 are substantially parallel to one another. Other, lowerfriction geometries are also contemplated such as that shown at 422 inFIG. 5b. Inner wall 430 is disposed at an oblique angle relative toouter wall 438 such that the distance between the inner wall and theouter wall increases with the distance from the fold 423 in the rollingsheath. The increased separation between the walls reduces the contactbetween the walls and hence the frictional interactions between thewalls.

Although the use of a flush lumen has only been shown in the embodimentof FIG. 4, it is understood that a flush lumen may suitably be used inany of the other embodiments disclosed herein.

Additional details of the design of embodiments of the inventive medicaldevice delivery system which employ collapsible midshaft sheaths, inparticular the portion of the device proximal to the rolling retractablesheath, may be found in the various embodiments disclosed in U.S. Pat.No. 5,534,007 to St. Germain and Olson, incorporated herein in itsentirety by reference.

In addition to the use of a collapsible midshaft sheath retractiondevice for retracting the outer sheath, the invention also contemplatesthe use of other suitable retraction means as are known in the artincluding slidably sealed retractable sheaths and midshaft seals asdescribed in co-pending commonly assigned U.S. patent application Ser.No. 08/722,834 filed Sep. 27, 1996, and a continuation-in-partapplication 09/071,484 filed May 1, 1998. The entire contents of bothapplications are hereby incorporated in their entirety by reference.Other contemplated retraction means include sheaths activated directlyby pull-collars as described in U.S. patent application Ser. No.09/071,484 filed May 27, 1998, and screw-like retraction devices asdescribed in U.S. Pat. No. 5,201,757 to Heyn et al. all of which areincorporated herein in their entirety by reference.

Alternatively, the rolling retractable sheath may be a full lengthsheath which extends to the proximal end of the medical device deliverysystem.

In yet another embodiment the invention, as shown generally in FIG. 6,the medical device delivery system comprises a rolling retractablesheath 522 closed on itself. The delivery system comprises an inner tube514 having a medical device mounting region 518 at the distal region forconcentrically mounting a medical device thereon. The proximal end ofrolling retractable sheath 522 is secured to the inner tube via optionalbumper 572 at a location 523 proximal to medical device mounting region518. If optional bumper 572 is not present, rolling retractable sheath522 may be secured directly to the inner tube. Rolling retractablesheath 522 contains stent 558 which is mounted over or around distal end518 of inner tube 514. Depending on the type of stent used, the stentmay alternatively be mounted directly on the inner tube. The distal endof rolling retractable sheath 522 is attached to a retraction device526. Adhesives such as polyurethane, epoxy, cyanoacrylates and acrylicsor other suitable means of attachment including heat welding, suturingor other forms of mechanically joining may be used to affix the rollingsheath to the retraction device. As shown in FIG. 6, retraction device526 is an outer sheath which covers the rolling sheath and extends in aproximal direction. Rolling retractable sheath 522 may be retracted bypulling outer sheath 526 in a proximal direction.

Rolling retractable sheath 522 may optionally be provided withlongitudinally oriented ribs to provide resistance to buckling.Similarly, a tapered sheath design similar to that shown in FIG. 5b andclosed on itself at both ends may also be used in order to preventbuckling of the sheath upon retraction of the sheath.

Outer sheath 526 may be a full length sheath which extends all the wayto the proximal end of the medical device delivery system oralternatively may extend proximally for only a portion of the deliverysystem. In the latter case, outer sheath 526 may be used in conjunctionwith a collapsible midshaft sheath as disclosed above.

The outer sheath may be made of a homogeneous polymer or a composite.Suitable materials include polyolefin copolymers, Pebax, polyurethane,nylon, polyethylene, polyesters and other thermoplastic elastomers. Itis desirable for the outer sheath to be flexible, but radiallynon-compliant. Optionally, the outer sheath may be formed of a polymerencapsulated braid or coil. The braid/coil may be formed of stainlesssteel encased in a polymer such as Polyimide with an inner layer ofTeflon™. Where the outer sheath is made of a polymeric tube, slits maybe made in the tube to increase the flexibility of the tube withoutsacrificing radial strength. The outer sheath may be made from amaterial which is chosen so as to provide support for the rolling sheathas it is retracted, to prevent distention of the rolling sheath.

Another suitable retraction device is a collar and pull wire. A pullcollar, as disclosed above, may be affixed to the distal end of therolling retractable sheath. A pull wire extending proximally from thepull collar may then be used to retract the rolling sheath. The pullwire may enter the inner tube at a point proximal to the stent andpreferably at a point which is at a distance of at least one rollingretractable sheath proximal to the stent so as not interfere with theoperation of the rolling sheath.

As discussed above, in conjunction with several of the otherembodiments, the rolling sheath may be formed of one material or may beformed of several materials joined together. Because, however, both theinner and outer walls of the rolling sheath roll in this embodiment, itis desirable that both the outer and inner walls be made of the samematerials.

As in the other embodiments of the invention, lubricants may be used inthe interior of the rolling retractable sheath in the embodiment of FIG.6 to reduce the frictional interactions between the walls of the sheathand to facilitate rolling. Any of the above lubricants may be employed.

A further advantage of the medical device delivery system shown in FIG.6 is the reduced length of the rolling sheath upon retraction ascompared with rolling sheaths that are not closed on themselves as inthe previous embodiments. Whereas the length of a rolling sheath closedon itself is unchanged upon retraction of the sheath, standard rollingsheaths may double in length upon retraction as the sheath is fullyextended and ceases to form a double layer. The reduced length of thefully retracted rolling sheath which is closed on itself as comparedwith a standard rolling sheath allows for a medical device deliverysystem of lower profile over a greater portion of the distal end of thesystem.

As shown in FIGS. 7a-d, the invention is directed to medical devicedelivery systems comprising an inner tube 614 with a medical devicemounting region 618 at the distal region for concentrically mounting amedical device 658 thereon, a rolling retractable sheath 622 forretaining medical device 658 on medical device mounting region 618 and aretraction device (not shown) for retracting the rolling sheath. Asfurther shown in FIGS. 7a-d, medical device mounting region 618 ischaracterized by a medical device mounting length, L_(m). Rollingretractable sheath 622 is disposed about inner tube 614 with theproximal end of rolling sheath 622 secured to inner tube 614 proximal ofthe medical device mounting region 618. Rolling sheath 622 in anunretracted state, as shown in FIGS. 7a and 7 c, is characterized by afirst length, L₁, as defined by the distance between the proximal-mostpoint on the unretracted sheath and the distal-most point on theunretracted sheath. Rolling sheath 622 in the unretracted state isfurther characterized by a double wall length L_(d) as measured by thelength over which the sheath forms a double wall. Rolling sheath 622upon retraction, as shown in FIGS. 7b and 7 d, is characterized by asecond length, L₂, as defined by the distance between the proximal-mostpoint on the retracted sheath and the distal-most point on the retractedsheath. Finally, rolling sheath 622 is operably connected to aretraction device (not shown) for retraction of the rolling sheath.

The delivery system is further characterized in that the differencebetween the second length L₂ and the first length L₁ is less than themedical device mounting length L_(m). Desirably the difference betweenthe second length L₂ and the first length L₁ will be less than half ofthe medical device mounting length. More desirably, the differencebetween the second length L₂ and the first length L₁ will besubstantially equal to zero as in FIGS. 7c and 7 d where the rollingsheath is closed on itself or where the sheath has a very short doublewalled region L_(d) as in FIGS. 7a and 7 b. It is also desirable for thesecond length L₂ to be less than twice the first length L₁ and/or lessthan twice the medical device mounting length L_(m).

Although in a preferred embodiment, the above-disclosed inventivemedical devices are used for delivery of self-expanding stents such asthat shown in FIG. 8 at 758, other stents may also be used inconjunction with this invention including mechanically expandable stentssuch as balloon expandable stents. A balloon is provided in the medicaldevice mounting region of the delivery device and a stent mountedthereon. Suitable inflation means as are known in the art, such as aninflation lumen, are provided. Other suitable medical device for usewith the present invention include grafts, including that shown in FIG.9 at 858 and vena cava filters, including that shown in FIG. 10 at 958.

While the medical devices have been described above as beingconcentrically mounted about the medical device mounting region of theinner tube, the invention is not intended to be so limited. Theinvention is directly more generally at a medical device delivery systemwith a medical device mounted about the medical device receiving region,whether or not the medical device is concentric with the inner tube.Moreover, the term ‘mounted’ as used in the context of the medicaldevice being mounted on the medical device receiving region is intendedto include the case where the medical device is in contact with themedical device receiving region of the inner tube as well as the casewhere the medical device surrounds at least a portion of the medicaldevice mounting region although it is not actually in contact with saidregion of the inner tube. An example of the former is as a stent crimpedonto the inner tube while an example of the latter is a self expandingstent which is maintained in place about the inner tube by a sheath.

Further, although the rolling retractable sheath has been referred to asbeing disposed concentrically about the inner tube, the inventionfurther contemplates the possibility of the rolling retractable sheathbeing disposed non-concentrically about the inner tube.

The present invention is also directed to methods of delivering amedical device, such as those described above, to a desired bodilylocation using any of the inventive devices described herein. One suchmethod comprises the steps of providing one of the above-describedmedical device delivery systems and a medical device and mounting themedical device on the medical device mounting region of the system. Themedical device delivery system is then percutaneously inserted in abodily lumen containing a bodily fluid. Where the sheath is made of aporous material, bodily fluids may pass through the sheath so as toself-prime the medical device delivery system. The medical device istraversed through the bodily lumen until the desired bodily location isreached at which point the rolling retractable sheath is retractedproximally so as to expose the medical device. The medical devicedelivery system is then withdrawn from the bodily lumen.

In particular, this method may be used to deliver a self-expanding stentto a desired bodily location. Upon retraction of the sheath, the stentself-expands and the delivery system is then withdrawn. FIG. 6 shows onesuch suitable stent 458 for use with the present invention. Othermedical devices such as balloon or mechanically expandable stents maysimilarly be delivered and deployed. In this case of the balloonexpandable stent, the delivery system must be modified to include aballoon mounted over the inner tube and under at least a portion of thestent and to further include suitable tubes to allow for inflation ofthe balloon, as is well known in the art. Other medical devices that maybe delivered by using the above method include grafts and vena cavafilters.

While several specific embodiments of the present invention have beendescribed, the invention is directed more generally toward the use ofrolling membranes in the manner described above in any other suitablecatheter design not specifically described herein includingover-the-wire, fixed-wire and rapid-exchange catheters.

In an over-the-wire embodiment, the inner tube extends proximally to amanifold and a guide wire may be inserted into the inner tube from theproximal end, the guide wire extending to the distal end of the system.The medical device delivery system may then ride on the guidewire.

In the case of the fixed-wire design, the guidewire is fixedly attachedto the medical device delivery system. A fixed-wire delivery system isdescribed in U.S. Pat. No. 5,702,364 to Euteneuer et al., incorporatedherein in its entirety by reference, and may be suitably modified foruse with the inventive medical device delivery system.

Similarly, a rapid exchange delivery system is described in U.S. Pat.No. 5,534,007 to St. Germain et al., incorporated herein in its entiretyby reference, and may be suitably modified for use with the inventivemedical device delivery system. Specifically, the rapid-exchange versionmay be realized by having the inner tube terminate in a guide wire portin a location along the system distal to the proximal end of the systemto allow for insertion of a guide wire therein. In the rapid-exchangeembodiment, only a portion of the medical device delivery system rideson a guidewire. Typically, the usable length of the medical devicedelivery system is approximately 135 cm. For a rapid-exchange medicaldevice delivery system, the distance from where the guide wire accessesthe inner tube to the distal tip will be approximately 5 cm to 45 cm.

The above Examples and disclosure are intended to be illustrative andnot exhaustive. These examples and description will suggest manyvariations and alternatives to one of ordinary skill in this art. Allthese alternatives and variations are intended to be included within thescope of the attached claims. Those familiar with the art may recognizeother equivalents to the specific embodiments described herein whichequivalents are also intended to be encompassed by the claims attachedhereto.

What is claimed is as follows:
 1. A medical device delivery systemcomprising: an inner tube, having a distal region and a proximal region,the inner tube having a medical device mounting region at the distalregion for mounting a medical device thereon, a rolling retractablesheath for retaining a medical device on the inner tube, the sheathhaving a proximal end and a distal end, the sheath disposed about theinner tube, the sheath including a rolling double walled member, thedouble walled member having an inner wall attached to the inner tubeproximal to the medical device mounting region and an outer wall, theinner wall made of a first material, the outer wall made of a secondmaterial, the second material different from the first material, theinner wall extending upward and attached to the outer wall, the sheathin the delivery position covering at least a portion of the medicaldevice mounting region.
 2. The medical device delivery system of claim 1further comprising a retraction device operably connected to the outerwall of the rolling retractable sheath for retraction of the retractablesheath, the retraction device moving the outer wall in a proximaldirection relative to the inner wall to expose a medical device mountingregion.
 3. The medical device delivery system of claim 1 wherein theinner and outer walls are adhesively bonded together at an end of therolling double walled member.
 4. The medical device delivery system ofclaim 1 wherein the inner and outer walls are mechanically joinedtogether at an end of the rolling double walled member.
 5. The medicaldevice delivery system of claim 1 wherein the first material rolls onretraction of the sheath and the second material does not roll onretraction.
 6. The medical device delivery system of claim 5 wherein thesecond material has a higher hoop strength than the first material. 7.The medical device delivery system of claim 5 wherein the outer wall ofthe sheath in the unretracted position has a higher tensile strengththan the inner wall of the sheath.
 8. The medical device delivery systemof claim 1 wherein the outer wall of the sheath and the inner wall ofthe sheath are made of the same material, the outer wall thicker thanthe inner wall.
 9. The medical device delivery system of claim 1 whereinthe outer wall of the sheath is thicker than the inner wall of thesheath.
 10. The medical device delivery system of claim 1 wherein theouter wall of the sheath is thinner than the inner wall of the sheath.11. The medical device delivery system of claim 1 wherein the inner andouter walls of the sheath are obliquely disposed relative to each other.12. The medical device delivery system of claim 1 wherein one or more ofthe inner and outer walls is formed of a porous material.